This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-36474 filed on Feb. 14, 2001.
1. Field of the Invention
The present invention relates to a sealing surface pressure increasing arrangement of a fluid conducting system, which is capable of increasing a sealing surface pressure around a connection between fluid passages in the fluid conducting system. More particularly, the present invention relates to a sealing surface pressure increasing arrangement of a fuel injection nozzle of an internal combustion engine.
2. Description of Related Art
The present invention relates to a sealing surface pressure increasing arrangement of a fluid conducting system, which is capable of increasing a sealing surface pressure around a connection between fluid passages in the fluid conducting system. More particularly, the present invention relates to a sealing surface pressure increasing arrangement of a fuel injection nozzle of an internal combustion engine.
One previously proposed fuel injection nozzle 100 of an internal combustion engine is provided in each cylinder of the internal combustion engine. With reference to FIGS. 3 to 4C, the fuel injection nozzle 100 has a retaining nut 104. The retaining nut 104 makes tight sealing contact of a contact surface between a nozzle body 101 and a tip packing 103 and also makes tight sealing contact of a contact surface between the tip packing 103 and a nozzle holder 102 by applying a predetermined axial fastening force to these contact surfaces. In the fuel injection nozzle 100, there is no particular structure for achieving the tight contact in these contact surfaces, and the tight sealing contact is achieved only by applying the predetermined axial fastening force to the contact surfaces from the retaining nut 104.
The tip packing 103 includes pin holes 111, 112 and a fuel relay passage 108. The pin holes 111, 112 receive corresponding positioning pins for positioning between the nozzle body 101 and the nozzle holder 102. The fuel relay passage 108 communicates a pressure chamber 105 and a fuel feed passage 106 of the nozzle body 101 to a fuel supply passage 107 of the nozzle holder 102.
The nozzle holder 102 has a leakage recovery passage 109. The leakage recovery passage 109 recovers fuel leaked through the contact surface of the nozzle holder 102 and through the contact surface of the tip packing 103 and conducts the leaked fuel to a low-pressure pipeline system. One end of the leakage recovery passage 109, which is located adjacent to the contact surface of the nozzle holder 102, is communicated with another leakage recovery passage 110. This leakage recovery passage 110 communicates an axial bore 115 of the tip packing 103 and an axial bore 116 of the nozzle holder 102 to the leakage recovery passage 109.
In recent years, fuel injection pressure of a fuel injection nozzle of a diesel engine has been progressively increased. Thus, there is a demand for increasing a sealing surface pressure between the contact surfaces of the components by increasing the axial fastening force of the retaining nut. However, when the contact surface of the nozzle body and the contact surface of the nozzle holder are fastened together via the tip packing by fastening or tightening the retaining nut, a frictional force generated between a shoulder of the nozzle body and an inner seat surface of the retaining nut upon application of the axial fastening force induces twist of the nozzle body. The twist of the nozzle body, in turn, causes a reduction of a roundness of a sliding portion of a nozzle needle and can finally prevents smooth sliding movement of the nozzle needle.
Thus, the increase of the sealing surface pressure achieved by increasing the axial fastening force of the retaining nut poses various disadvantages in terms of deformation and strength of the components, such as the nozzle body. Furthermore, the arrangement that increases the sealing surface pressure of the components by increasing the axial fastening force of the retaining nut poses a disadvantage in terms of manufacturing costs.
Thus, it is an objective of the present invention to provide a sealing surface pressure increasing arrangement of a fluid conducting system capable of increasing a sealing surface pressure around a connection between fluid passages without substantially increasing an axial fastening force applied to the connection.
To achieve the objective of the present invention, there is provided a sealing surface pressure increasing arrangement of a fluid conducting system. The arrangement includes a first fluid conducting component, a second fluid conducting component and a third fluid conducting component. The first fluid conducting component has a first fluid passage therein. The second fluid conducting component has a second fluid passage therein. The third fluid conducting component is clamped between the first fluid conducting component and the second fluid conducting component and has a third fluid passage for communicating between the first fluid passage and the second fluid passage. At least one reduced thickness portion in a form of a recess is provided in at least one of a first contact surface between the first fluid conducting component and the third fluid conducting component and a second contact surface between the second fluid conducting component and the third fluid conducting component, so that a sealing surface area of the at least one of the first and second contact surfaces is reduced to increase a sealing surface pressure in the at least one of the first and second contact surfaces around at least one of the fluid passages.